1. Field of the Invention
The present invention relates to a halogen-free flameproof mesh sheet suitable for being used outdoors such as at a construction work site for a extended period of time, as well as to flame retardant compositions and methods for their manufacture and use.
2. Description of Related Art
In recent years, there has been a trend toward the construction of buildings having a large number of stories in the construction industry. Meanwhile, there has also been an increase in the number of houses having a small number of stories. Different types of flameproof mesh sheets are often used in the construction industry for safety and protection. Flameproof mesh sheets such as those useful for houses having a small number of stories and/or sheets used for scattering prevention must be laid in these buildings and regulations of such sheets are becoming more and more strict.
Currently used flameproof mesh sheets are produced by weaving gray yarn prepared by coating a polyester, nylon or polypropylene multi-filament fiber with a vinyl chloride-based paste resin composition and heating the obtained gray cloth. Alternatively, such sheets are made by coating a woven gray fabric prepared from multi-filament fibers with a vinyl chloride-based paste resin composition. The coated fabric is heated and processed to a desired shape.
Typical resin compositions for coating fibers and fabrics comprise a chlorine containing vinyl chloride resin and a chlorine-based flame retardant such as chlorinated paraffin. It is also possible to employ a brominated flame retardant such as decabromodiphenyl oxide or an inorganic flame retardant such as antimony trioxide (known coating compositions are disclosed, for example, in examined Japanese Patent Publication Nos. 52-41786, 53-18065 and 61-9430, as well as Plastics, February, 1991 which are incorporated by reference in their entireties.
Throughout the world, in recent years, limitations on the use of resins and flame retardants containing halogen which generate harmful gases (such as dioxins and bromine dioxins) at the time of combustion have been put into place from the viewpoint of the environmental preservation of the earth.
It has been proposed in Japanese Laid-open Patent Application No. 10-199406 a flame retardant for mesh sheets which comprises ammonium polyphosphate, as well as a flameproof mesh sheet comprising the same. This invention is halogen free and excellent in terms of no increase in viscosity during storage. However, when the mesh sheet is washed and used repeatedly, a tendency toward the elution of ammonium polyphosphate is seen.